Light image forming materials can be used in many purposes, for example, as proof paper, print-out paper, overlay film or so on. There have so far been many photographical applications of the so-called free radical photographic materials which have areas visualized by imagewise exposure.
A method which is especially effective in those radical type photographic materials consists in converting various kinds of leuco dyes to their corresponding dyes by the use of photo oxidizing agents, and thereby achieving color development through radical oxidation.
However, since such combinations of leuco dyes with photo oxidizing agents are sensitive to light, color formation occurs by exposure to ordinary room light, sun light or white light even after dye images have been formed by imagewise exposure. Accordingly, there is difficulty in handling light image forming materials of this type.
In order to retain images after they have once been formed, it is necessary to avoid further color development in areas not having been exposed to light at the time of imagewise exposure. For instance, it is known to keep original images by applying a reducing agent solution, such as that of a free radical capturing substance, to the materials having images formed therein by a spraying or a dipping process. However, such a wet process leaves a large question in respect that it is attended by complexities of working and procedures. As another instance, there is a process proposed in JP-A-47-12879 (the term "JP-A" as used herein mean an "unexamined published Japanese patent application") (corresponding to U.S. Pat. No. 3,658,543), wherein images are formed by means of UV rays, and then fixed through activation of photoreducing substances by means of visible light. However, this process also leaves a serious question in that the apparatus is occupied by one image-forming material throughout the light exposure carried out twice, and replacement of one spectral filter with another is required for proper use of two kinds of light. On the other hand, JP-B-43-29407 (the term "JP-B" as used herein means an "examined Japanese patent publication") proposes a process in which a reductive thermofixer is incorporated into or coated on a light-sensitive layer, and thermal fixation is carried out after imagewise exposure. However, this process also has a weighty question that since a light susceptible component (including leuco dyes and photo oxidizing agents) is present in the vicinity of the fixer, a decrease in sensitivity with the lapse of time takes place. In addition, the light image forming compositions described above are coated on a support using an organic solvent, so measures for prevention of explosion are required of the production equipment, and the use of organic solvent causes a further disadvantage in both safety and cost.
With the intention of solving those questions, we have found a fixable type light image forming material in which a combination of a leuco dye and a photo oxidizing agent is contained in microencapsulated condition, and a reducing agent is present o the outside of these microcapsules (see U.S. patent application Ser. No. 07/257,580 filed on Oct. 14, 1988).
However, even the light image forming material of this type has turned out to have a problem that because of insufficient water-resisting property of the light image forming layer, in wiping up water drops attached to the layer surface, the coated layer is likewise wiped off, or the coated layer is easily delaminated by a long-range exposure to water or soaking in water for a long time.